Coronilla - Crown Vetch, Scorpion Senna
DESCRIPTION: This group consists of about fifty-five hardy and tender shrubs and annual or perennial herbaceous plants. They are found in the Mediterranean region, Africa, the Canary Isles, China, and northern Asia. These plants, commonly known as Crown Vetch, range in height from 1 to 9 feet. Their leaves are deeply cut and they bear bunches of purple, yellow, red or purplish-pink, pea-shaped flowers, in the summer. They are great for the rock garden, border or greenhouse. C. emerus (Scorpion Senna) is a hardy, medium-sized, deciduous shrub with clusters of yellow flowers borne in the axils of the leaves. The blossoms are followed by seedpods that are shaped like a scorpion's tail, thus the common name. C. valentina subsp. glauca is a tender, small to medium sized shrub that is suitable for growing in a sheltered position, such as against a warm wall. It has bloomy leaves and a profusion of yellow blossoms that smell like peaches. It mostly flowers in mid-spring, though it blooms off and on throughout most of the year.
POTTING: These plants grow best in well-drained, light, sandy, loamy soil, in a sunny location. They need a minimum temperature of 45º F. They can be watered freely throughout the summer, but less often other times. Pruning consist of cutting away dead or weak growth, in late winter. Old plants that aren't producing flowers freely, can be rejuvenated by cutting back close to ground level.
PROPAGATION: In March and April, seeds can be sown in a greenhouse having a 60º to 65º F temperature in pots of sandy soil. The seedlings should be potted in 3-inch pots filled with sandy loam and leaf mold. They are then placed in a cold frame until May. The hardy kinds can be planted outside in a sunny place in the rock garden. Pinch the tips of the young plants to encourage bushy growth. Those that are going to be used to decorate the greenhouse should be planted in 5- or 6-inch pots filled with equal parts fibrous loam and leaf mold. Cuttings, 3-4 inches long, can be taken in June and inserted in a cold frame. They should form roots in four or five weeks; they are potted separately in 3-inch pots and wintered in a greenhouse or frame in a minimum temperature of 45º F. In March or April, they're planted outside or repotted for the greenhouse.
VARIETIES: C. emerus; C. valentina & var. glauca, Citrina, Variegata; C. montana (shrubby); C. glauca (evergreen bush); C. viminalis (trailing shrub); C. cappadocica; C. varia. (The latter two are rock garden trailing plants and C. varia is hardy and is naturalized in northeastern North America.)
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